1. Field of the Invention
The present invention relates to a printing method, a printing apparatus, and a printed document as a resulting printed matter by which liquid ink is applied to a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet including minute concave section and convex section to print an image.
In particular, the present invention relates to preferred printing method, printing apparatus, and printed document as a resulting printed matter used to print an image on a superposed surface as an information-supporting face of an information-supporting sheet. The information-supporting sheet includes, for example, a folded sheet in which a superposed surface obtained by folding or a cutting is used as the information-supporting face, an information communication sheet having confidentiality like the one provided by a superposed sheet, or an information communication sheet such as an organizing sheet that can have an enlarged size.
2. Description of the Related Art
In the information-supporting sheet in which information is supported by superposed surfaces of a superposed base sheet, the superposed surfaces generally have thereon pressure-sensitive adhesive layers of pressure-sensitive adhesive agent so that the superposed surfaces can be adhered to each other in a peelable manner. The pressure-sensitive adhesive layers are formed on the entire face or a specific part of the surfaces to be superposed, and are formed in a predetermined pattern or linear form so that the pressure-sensitive adhesive layers can be opposed to each other when the surfaces are superposed together. This pressure-sensitive adhesive agent is also called as autohesion pressure-sensitive adhesive agent. When the pressure-sensitive adhesive layers made of pressure-sensitive adhesive agent are strongly pressurized to each other, polymers in these pressure-sensitive adhesive layers adhere to one another by the self-diffusion. By selecting the type of composition or the level of pressurization of the pressure-sensitive adhesive agent, permanent adhesiveness or peelable adhesiveness is achieved. The information-supporting sheet having a peelable superposed surface also may be called as a “pressure-sensitive adhesive sheet” hereinafter.
Recently, the inkjet printing method has been increasingly used as a method to print an address, a name, and individual information on the superposed surface of the pressure-sensitive adhesive sheet. In particular, the diffusion of color ink has enabled a high-level color printing (process printing) equal to a conventional printmaking technique.
In the pressure-sensitive adhesive sheet as described above, the superposed surfaces on which information is printed are adhered to each other by the pressure-sensitive adhesive layer to subsequently peel these superposed surfaces. This peeling process has caused some cases where information printed on one superposed surface is transferred onto the other superposed surface (hereinafter referred to as “ink offset”). Such an ink offset also may be caused in the use of the inkjet printing method. When ink used for the inkjet printing method is water-soluble dye ink, a printed image may have an insufficient water resistance.
In order to prevent them, Japanese Patent Laid-Open No. 11-48651, Japanese Patent Laid-Open No. 11-334201, and Japanese Patent Laid-Open No. 09-058118 suggest a method to add a cationic compound to the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet used for the inkjet printing method and a method to use ink including pigment having a superior water resistance as a main component for example.
However, even the methods as described above find it difficult to prevent the ink offset. Thus, when ink including a pigment having a superior water resistance as a main component is used, the ink offset is more apparent. The addition of a cationic compound also has caused some cases where the pressure-sensitive adhesive layer is caused to include gel-like coating liquid, preventing the coating of the coating liquid. Another problem is that a wet offset printing may cause the elution of cation resin to cause a dirty printing plate.